This invention relates to a cleaning apparatus and an image formation apparatus and more particularly to a cleaning apparatus placed in the proximity of a surface of an image support with a toner image formed on the surface and an image formation apparatus for transferring the toner image formed on the image support to a recording medium and executing thermal fixing for the recording medium onto which the toner image is transferred by a thermal fuser for forming an image on the recording medium.
Generally, in an image formation apparatus using electrophotography, a cleaning apparatus for cleaning residual toner on an image support is installed in the proximity of the image support. As the cleaning apparatus, a cleaning apparatus of an integral type comprising a cleaning member for cleaning residual toner on an image support, a housing formed with an opening toward the image support, and a seal member being held on the housing for guiding the cleaned toner into the housing in one piece is widely used from the advantages of costs, productivity, maintenance, etc. It is required that the cleaning member and the seal member be positioned with respect to the image support with high accuracy; the integral-type cleaning apparatus is also advantageous from the viewpoints of high-accuracy design and accuracy control.
Particularly in a color image formation apparatus springing into wide use in recent years, generally it is necessary to overlay color toners of yellow, magenta, cyan, and black on each other. For example, in an image formation apparatus using an intermediate transfer body, the four colors are overlaid on the intermediate transfer body. At this time, a cleaning apparatus must be out of contact with the intermediate transfer body. After four color toner images are transferred to a recording medium, such as paper, in batch, the cleaning apparatus abuts the intermediate transfer body for cleaning residual toner.
Thus, the cleaning apparatus of the color image formation apparatus needs to be brought into contact with or out of contact with the intermediate transfer body, and becomes inferior to a fixed cleaning apparatus of a single-color image formation apparatus in position accuracy relative to the cleaned surface. Then, to compensate for degradation of position accuracy, higher accuracy is required for the cleaning apparatus itself, namely, the dimensions, etc., of a cleaning member and a seal member.
However, in a high-density image formation apparatus such as a recent color laser beam printer, often a cleaning apparatus must be installed at a position near a thermal fuser. In this case, the cleaning apparatus is heated and is thermally expanded by heat-generated from the thermal fuser.
Particularly, a housing of a cleaning apparatus usually is formed of a plastic resin and has a large expansion amount. If such a housing differs from a cleaning member and a seal member in thermal expansion coefficient, a force occurs in the retention portions of the cleaning member and the seal member in the housing and warps or distorts the cleaning member and the seal member. Thus, it is feared that a problem of a cleaning failure or toner scattering may arise. Particularly, the seal member usually is formed of urethane, polyethylene terephthalate, etc., like a film; it is feared that shape change such as warp or distortion may be caused if a slight force occurs in the retention portion of the seal member.
As trouble caused by heat from a thermal fuser, toner in a cleaning apparatus near the thermal fuser is solidified. To prevent toner from being solidified, generally a fan for releasing heat generated from the thermal fuser into the outside and cooling the thermal fuser and its peripheral devices is installed aside from a fan for cooling an optical scanner, a photosensitive body, a developing apparatus, etc.
Hitherto, just after power of the image formation apparatus is turned on or when the thermal fuser reaches a preset fixing temperature, the two fans start to turn and cool the thermal fuser, the optical scanner, the photosensitive body, the developing apparatus, etc.
In the above-described control, however, if the image formation apparatus is installed in poor temperature and humidity environments, condensation may occur on the photosensitive body, etc. If the two fans start to cool the components in the condensation occurrence state, temperature in the image formation apparatus does not much arise and it is feared that image formation processing may be started with condensation left. In this case, print image quality is degraded and it is feared that a current may leak through water drops, causing trouble such as breakage of the image formation apparatus.
To cope with such condensation occurrence, the Unexamined Japanese Patent Application Publication No. Hei 9-292820 discloses an art for preventing condensation by stopping fans until the inside of a apparatus is warmed after power is turned on.
However, if the fans remain stopped, the periphery of a thermal fuser reaches a high temperature and a problem of solidifying toner in a cleaning apparatus again arises.